/**
 * Created by zhang on 2015-03-18.
 */
"use strict";

/**
 * 对于未初始化和未声明的变量执行typeof操作  返回undefined
 * @type {string}
 */
    function setundefined(){
        var str ="";
        var un;
        var mess = undefined;
        alert(typeof str);
        alert (typeof un); //undefined
        alert (typeof mess); //undefined
        alert(typeof age);
    }
//unde();
/**
 * 保存对象的变量还没有真正的保存对象，应该明确的让变量保存null值
 * @type {null}
 */
    function setNull(){
        var car = null;
        alert(typeof car);
        alert(null == undefined);
    }

